Welded, Laminated Apparatus, Methods of Making, and Methods of Using the Apparatus

ABSTRACT

The invention describes methods of welding onto laminated devices using a low temperature welding process. Also described are laminated devices with welds that do not disrupt a brazed core block of sheets in the laminated devices. Novel laminated devices with welded features for servicing the devices are also described.

RELATED APPLICATIONS

This application claims priority to U.S. provisional patent application61/309,851, filed 2 Mar. 2010.

INTRODUCTION

Laminated devices are often formed by brazing together metal sheets,using an added material (braze) interlayer between adjacent sheets inorder to achieve adhesion and or joining and or a substantially hermeticseal between two or more layers. A problem with welding an additionalpiece on to such a laminated device in proximity to braze boundarylayers is that conventional welding often results in cracks that formbetween the sheets. Laminated apparatus, especially microchannelapparatus can be deformed or weakened by welding processes. Thus, thereis a need for methods repairing cracks in laminated apparatus and alsofor laminated apparatus that is less susceptible to cracking.

SUMMARY OF THE INVENTION

In one aspect, the invention comprises a method of welding a metal ontolaminated apparatus, comprising: providing laminated apparatuscomprising sheets of metal bonded together, at least in part, by a brazecomposition disposed between the sheets; applying a metal onto thelaminated apparatus by a welding technique wherein a wire moves in areciprocating motion (moving alternatively back and forth) and wherein aspark is generated when the wire touches and/or is pulling away from thelaminated apparatus and wherein molten metal is applied to the surfacewhile the wire moves away from the surface. Typically, the process iscarried out in an inert atmosphere such as by a shroud of inert gasblowing around the wire and apparatus. It may be the case that a brazecomposition is present between all the sheets; however, in some devices,there is a braze composition only between some sheets—this could be thecase, for example, where some sheets are prebonded by diffusion bonding(to form a subassembly) and the resulting diffusion-bonded laminatedpieces are subsequently joined to single sheets or anotherdiffusion-bonded laminated piece by brazing.

In some alternative embodiments, the method can be characterized asintermittent arc discharge with a reciprocating welding wire. Likewise,molten metal is applied to the surface while the wire moves away fromthe surface.

Further, the method could be used to weld a solid metal article to abrazed, laminated structure. The solid article could be a header, afooter, and inlet or outlet nozzle, an enclosure (see below), astructural support element useful either during operation or in aambient state, a connector used for lifting or supporting the laminateddevice, or other useful component.

This process can be conducted with very low heating of the laminatedapparatus and, in preferred embodiments, within 30 seconds of activewelding (according to the inventive process) and without the applicationof liquid quenching, the temperature of the laminated article is 100° C.or less throughout the entire apparatus. In another embodiment, thetemperature of the laminated article is 50° C. or less within 30 secondsof completing the welding step. This contrasts with conventional weldingprocesses in which the laminated article is much hotter, typically redhot, during the welding and for several minutes after welding hasceased.

The inventive process enables the production of unique structures, andthe invention includes apparatus made by the inventive process.Generally, the process results in a structure in which there is littlediffusion, at the welding site, of welding composition into the coreblock. The core block comprises laminated sheets which have been joinedinto a stack. Core blocks may have more than 10 or more than 100 or morethan 1000 layers.

In addition, the invention provides welded, laminated apparatus. Thelaminated apparatus comprises: a core block comprising sheets of metalbonded together, at least in part, by a braze composition disposedbetween the sheets; a welding composition disposed on the core block andadhering to the braze composition; wherein the welding composition has acomposition that differs from the composition of the braze composition;and wherein the welding composition is diffused 2 mm or less (preferably1.0 mm or less, preferably 0.5 mm or less, more preferably 0.3 mm orless) into the core block. Typically, diffusion into the core block canbe measured by microscopy on a cross-section of the core block.

Preferably, the core block comprises sheets of metal bonded together, atleast in part, by a braze composition disposed between the sheets. Thecore block comprises stacked sheets, and may include manifolds that areintegral to the sheets, but the core block does not include externalmanifolds, handles, or external tubes.

In a further aspect, the invention provides microchannel apparatus,comprising: a core block comprising sheets of metal bonded together;plural microchannels disposed within the core block; the pluralmicrochannels comprising plural apertures on one side of the core block;a solid-walled enclosure that encloses the plural apertures within asingle, contiguous space; wherein the solid-walled enclosure comprises asolid, continuous wall that is welded on one side to the core block by aweld material; wherein the continuous wall has an aspect ratio of atleast 10:1 of height to thickness (where height is the direction thatthe wall projects from said one side of the core block, and thickness isperpendicular to height and is the commonly-used understanding of wallthickness.

The invention also includes any of the apparatus or methods described inthe section entitled Detailed Description of the Invention. For example,the invention includes a method in which a weld is formed over apertures(channel openings) and weld material is then removed to reopen thechannels (see Example 2). The invention also includes apparatus in whichsheets comprising channels protrude from a face of a core block (seeFIG. 3).

Advantages of the invention include the reduction or elimination ofleaks and cracks. The welding method is particularly useful forlaminated articles in which an interlayer has a melting point less thanthat of the laminated sheets, which have a higher melting point. Weldscan be made along cracks, parallel to layers within a laminate,perpendicular to layers within a laminate, or at any angle relative tolayers in a laminate. It is difficult to weld onto a block which hasbeen formed from brazing parallel sheets. This is because the brazingmaterial has a low melting point compared to the sheet material, whichis suitable for obtaining good brazing. During brazing, the brazematerial moves around and quite effectively fills the voids between thesheets. Subsequent welding onto a brazed article results in re-meltingof braze material in the warm location of the weld, resulting indiffusion of weld material into braze material. While not wishing to bebound by theory, when the article cools after welding, the welding andbrazing compositions may cool at different rates, and the materialjoining the sheets becomes non-uniform in that location, which may causecracks in the filler material between the sheets. These cracks interferewith the integrity of the device, which, if used for fluid processing,may result in leaks. These problems are magnified for devices with manylayers, and is also magnified for devices with longer dimensions, andlonger welds, all of which contribute to cracks, which either must bedetected and repaired, or the article scrapped. This invention avoidsthese problems by applying new welding techniques (e.g. CMT, with apassing reference to fiber laser welding) to minimize the diffusion ofweld composition into braze material in a brazed laminated article.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows weld seams.

FIG. 2 schematically illustrates a perspective view of a core block withan attached enclosure and a side view with an optional connectedmanifold enclosure and piping.

FIG. 3 shows coolant channels protruding out from coolant face in aFischer-Tropsch reactor core.

FIG. 4 is a view showing repaired braze seams on test FT reactor.

FIG. 5 is a view showing process face of small FT test reactor. Seams1-3 are within the waveform zones (central region) of the reactor. Seams4-9 are within the perimeter zones of the reactor.

FIGS. 6-8 illustrate welding methods of sealing leaks in a laminateddevice.

DETAILED DESCRIPTION OF THE INVENTION

The appearance of the weld seam on a part after welding along a laminateseam can have a distinct semicylinder or partial cylinder shape (seeFIG. 1). The region is typically fairly straight if it is made by arobotic or automated welding process, and in some preferred embodiments,the weld seam is substantially straight as illustrated in the figurebelow. The radius of the semicylinder that sits above the laminated partis typically less than 10 mm and preferably between 0.01 mm to 5 mm,with a more preferable range from 0.1 mm to 2 mm.

In some embodiments, the weld has the semicircular shape describedabove. The metal sheets have a composition that is different than thebraze interlayer. In some embodiments, the weld composition is differentfrom the composition of the metal sheets.

The invention includes microchannel apparatus schematically illustratedin FIG. 2., comprising: a core block 17 comprising sheets of metalbonded together; plural microchannels disposed within the core block;the plural microchannels comprising plural apertures 19 on at least oneside of the core block; a solid-walled enclosure 21 that encloses theplural apertures within a single, contiguous space 22; wherein thesolid-walled enclosure comprises a solid, continuous wall that is weldedon one side to the core block by a weld material 23; wherein thecontinuous wall has an aspect ratio of at least 10:1 of height tothickness (where height is the direction (corresponding to 21) that thewall projects from said one side of the core block, and thickness isperpendicular to height and is the commonly-used understanding of wallthickness); and wherein the side of the solid-walled enclosure that isopposite to the side that is welded to the core block may comprise aconnection to a conduit 27. The connection to the conduit 25 maycomprise a conventional weld, while the connection of the enclosure tothe core block is preferably an inventive weld of the type describedherein. Thus, typically, the connection to the conduit has a differentcomposition and/or morphology than the weld material. The conduit maycomprise piping 29. Preferably, the weld to the core block is formed byCold Metal Transfer (CMT) welding. The CMT weld may alternatively bedescribed in any of the ways provided herein. In less preferredembodiments, where the apparatus is used under low temperature and/orlow corrosion conditions, a header space can be formed via a gasketconnecting the enclosure with a conduit.

In addition to the use of CMT to join an enclosure to a brazed article,other low energy input methods of welding may be used to attach anenclosure or a header to a laminated device. For example, a fiber laser,such as with a Yb laser, may be used to join a solid metal article to abrazed article. The laser welding approach creates a narrow but deeppenetration weld that is particularly useful for creating a structuraljoint on a pressure or load bearing part.

The invention also includes methods of making laminated apparatuscomprising the use of CMT; preferably including CMT to weld theenclosure on the core block.

The apertures comprise inlets or outlets for fluid processing or portsused for instrumentation for process measurements and controls,diagnostics, or for use during manufacturing or refurbishment of theapparatus

The invention also includes methods of accessing the pluralmicrochannels through said plural apertures, comprising: breaking theconnection between the enclosure and a conduit without disrupting theweld that attaches the solid-walled enclosure to the core block, andaccessing the plural microchannels through the solid-walled enclosureand through the plural apertures.

The invention also includes reattaching the connection to re-attachedpiping.

After breaking the connection, tasks that could be conducted include:maintenance or inspection of the core block, including removing material(comprising for example, but not limited to catalyst, sorbents, fins,waveforms, and other inserted materials), adding material (catalyst,sorbents, fins, waveforms, inserts), and inspecting the quality anduniformity of the flow passages through diagnostic tests, including flowtests, and performing maintenance, such as cleaning or repair of thepassageways.

The enclosure is a solid metal ring that mates with the brazed surfaceand is then used for subsequent welding of headers or footers to bringor remove fluids to a microchannel brazed device. The solid ring may bea unitary (preferably made by molding) part or made from two or four ormore parts that are welded together to form a solid ring. In oneembodiment for a square or rectangular face, it is preferable to form aring using 4 straight parts with weld joints to form a contiguous squareor rectangular ring. The advantage of a ring (which may be circular,square, rectangular, or other shape) is that the header or footer may becut or ground off many times to have access to the channels afteroperation for catalyst refurbishment or for evaluation of changes tochannels or for a cleaning or defouling step after process operation. Itis envisioned that catalysts loaded in a microchannel device would beremoved periodically (from every week to once every 10 years) and atthat time, the header and or footer would need to be separated from thering for such refurbishment. The initial welding across braze seams orjoints or across laminates might only occur once in the life of a brazeddevice.

The inventive methods of servicing a laminated device providesignificant advantages over methods that can be conducted usingconventional apparatus (such as simple tub welds) since the aperturescan be accessed without damaging the surface of the core block.Additionally, since the weld between the enclosure and the conduit canbe removed by simple grinding (optionally vacuum grinding) rather thancutting; there is less contamination than conventional methods.

In some preferred embodiments of the invention, there is a weld acrossplural brazing layers (the layers between metal sheets). The weld can beparallel to the metal sheets, perpendicular to the metal sheets or atany desired angle with respect to metal sheets in a core block.

The invention also provides a method of using the any of theabove-described apparatus comprising passing a fluid through channels inthe core block, and a conducting a unit operation on the fluid as itpasses through the channels. The apparatus may be used for processessuch as heat exchange, mixing, heating, cooling (including a heat sinkfor electronic devices), chemical reaction, chemical separation. Theapparatus may also comprise an electrochemical device, which utilizes asolid or liquid electrolyte and electrodes to obtain electrical workfrom a spontaneous chemical reaction (including but not limited tobatteries and fuel cells), or conversely, to apply electrical work togenerate chemical species (including but not limited to eletrolyzers,oxygen generators and reverse fuel cells), or to produce an electricalsignal in response to a change in the device environment (including butnot limited to sensors and analytical devices). The apparatus may alsobe a thermoelectric device. In some preferred embodiments, the apparatusis a chemical reactor.

In preferred embodiments, sheet thicknesses are 1 cm or less (such asmay contain waveforms, engineered catalyst structures, fins, etc.), 2 mmor less, and in some embodiments 1 mm or less.

As used herein, the term “microchannel” refers to any conduit having atleast one dimension (height, length, or width) (wall-to-wall, notcounting catalyst) of 1 cm or less, including 2 mm or less (in someembodiments about 1.0 mm or less) and greater than 100 nm (preferablygreater than 1 μm), and in some embodiments 50 to 500 μm. Microchannelsare also defined by the presence of at least one inlet that is distinctfrom at least one outlet. Microchannels are not merely channels throughzeolites or mesoporous materials. The length of a microchannelcorresponds to the direction of flow through the microchannel.Microchannel height and width are substantially perpendicular to thedirection of flow of through the channel. In the case of a laminateddevice where a microchannel has two major surfaces (for example,surfaces formed by stacked and bonded sheets), the height is thedistance from major surface to major surface and width is perpendicularto height.

In some embodiments, the laminated apparatus may comprise one or morewaveforms. A “waveform” is a 3-dimensional contiguous piece of thermallyconductive material that at least partially defines one or moremicrochannels. The waveform may have a gap between the waves that is inthe microchannel dimension or may be larger. In exemplary form, this gapmay be in the microchannel dimension because then heat is easilytransferred to the long direction in the wave that separates the heattransfer channels before conducting down the more conductive wave formto the heat transfer channels. The waveform may be made of copper,aluminum, FeCrAlY, metals, oxides, or other materials. The waveformpreferably has a thermal conductivity greater than 1 W/m-K.

As is standard patent terminology, “comprising” means “including” andneither of these terms exclude the presence of additional or pluralcomponents. For example, where a device comprises a lamina, a sheet,etc., it should be understood that the inventive device may includemultiple laminae, sheets, etc. In alternative embodiments, the term“comprising” can be replaced by the more restrictive phrases “consistingessentially of” or “consisting of.”

“Unit operation” means chemical reaction, vaporization, compression,chemical separation, distillation, condensation, mixing, heating, orcooling. A “unit operation” does not mean merely fluid transport,although transport frequently occurs along with unit operations. In somepreferred embodiments, a unit operation is not merely mixing.

“A process of operating” means repairing, maintaining, refurbishing, ordiagnosing; and may include preparations conducted prior to conductingunit operations, scheduled or unscheduled maintenance, or other uses ofthe apparatus.

Microchannel apparatus (such as microchannel reactors) preferablyinclude microchannels (such as a plurality of microchannel reactionchannels) and a plurality of adjacent heat exchange microchannels. Theplurality of microchannels may contain, for example, 2, 10, 100, 1000 ormore channels capable of operating in parallel. In preferredembodiments, the microchannels are arranged in parallel arrays of planarmicrochannels, for example, at least 3 arrays of planar microchannels.In some preferred embodiments, multiple microchannel inlets areconnected to a common header and/or multiple microchannel outlets areconnected to a common footer. In some preferred embodiments, there maybe multiple separate flow streams. One fluid stream may flow through aplurality of microchannels. A second fluid stream may flow through asecond plurality of microchannels, or may flow through one or moremacrochannels. During operation, heat exchange microchannels (ifpresent) contain flowing heating and/or cooling fluids. Non-limitingexamples of this type of known reactor usable in the present inventioninclude those of the microcomponent sheet architecture variety (forexample, a laminate with microchannels) exemplified in U.S. Pat. Nos.6,200,536 and 6,219,973 (both of which are incorporated by reference).

In many preferred embodiments, the microchannel apparatus containsmultiple microchannels, preferably groups of at least 5, more preferablyat least 10, parallel channels that are connected in a common manifoldthat is integral to the device (not a subsequently-attached tube) wherethe common manifold includes a feature or features that tend to equalizeflow through the channels connected to the manifold. Examples of suchmanifolds are described in U.S. patent application Ser. No. 10/695,400,filed Oct. 27, 2003 which is incorporated herein. In this context,“parallel” does not necessarily mean straight, rather that the channelsconform to each other. In some preferred embodiments, a microchanneldevice includes at least three groups of parallel microchannels whereinthe channel within each group is connected to a common manifold (forexample, 4 groups of microchannels and 4 manifolds) and preferably whereeach common manifold includes a feature or features that tend toequalize flow through the channels connected to the manifold.

Microchannels can incorporate materials paced inside the microchannels,such as catalysts, sorbents, or other materials. Such materials may beincorporated into the channels as particulates or small piecesCatalysts, sorbents, or other coatings can be applied onto the interiorsurface of a microchannel using techniques that are known in the artsuch as wash coating. Techniques such as CVD or electroless plating mayalso be utilized. In some embodiments, impregnation with aqueous saltsis preferred. Pt, Rh, and/or Pd are preferred in some embodiments.Typically this is followed by heat treatment and activation steps as areknown in the art. Other coatings may include sol or slurry basedsolutions that contain a catalyst precursor and/or support. Coatingscould also include reactive methods of application to the wall such aselectroless plating or other surface fluid reactions.

The sheets of metal in a laminated apparatus are preferably a stainlesssteel or a superalloy, such as a nickel, cobalt, or iron basedsuperalloy. Other examples include, but are not limited to, FeCrAlY,titanium alloys, and Ni—Cr—W superalloy. Sheets typically range inthickness from 10 μm to 1 cm, more typically 100 μm to 5 mm. Sheets maybe solid (such as dividing walls) and may contains holes or slots aswell as partially etched channels and other features such as is known inthe art of laminated devices.

Prior to brazing surfaces are preferably cleaned and may be coated witha surface layer such as a Ni layer.

Materials for brazing are well known in the art. Brazing is typicallyconducted in vacuum or an inert atmosphere. As is well known, duringbrazing, a relatively low temperature brazing material is melted betweenmetal sheets and then some diffusion occurs between the brazing materialand the sheets and, after cooling, a braze composition (which typicallydiffers somewhat from the composition of the original brazing material)remains between the sheets. Techniques such as microscopy and otherknown metallurgical techniques can be used to identify and characterizea braze composition between sheets in a laminated device.

The present invention is generally applicable to brazed laminates. Fornickel-based metal sheets, a preferred brazing material is NiP. Onestandard braze material is BNi-6 or a combination of 10-12.5%Phosphorous in nickel. Brazing often uses a transient liquid phase (TLP)interlayer which acts as a melting point depressant for a metal. At anelevated temperature that exceeds the operational temperaturerequirement but does not approach the melting point of the parentmaterial or a temperature which contributes significant diffusionbonding or grain growth of metals across laminate shim boundaries, theTLP transforms from a solid to a liquid phase to flow and fill all voidsbetween layers. As the braze process occurs the TLP depressant material,which may be phosphorous or boron or others diffuses from the brazeinterlayer to change the melting point of the metal.

Some nonlimiting examples of brazing compositions include the followingeach of these braze interlayers would be advantaged by the describedinvention.

MBF AWS & AMS Nominal Composition, wt. % Alloy Classifications Cr Fe SiC* B P W Co Ni 15 13.0 4.2 4.5 0.03 2.8 — — 1.0* Bal 20 AWS BNi2/AMS4777 7.0 3.0 4.5 0.06 3.2 — — — Bal 30 AWS BNi3/AMS 4778 — — 4.5 0.063.2 — — — Ba 50 AWS BNi-5a 19.0 — 7.3 0.08 1.5 — — — Bal 51 AWS BNi-5b15.0 — 7.25 0.06 1.4 — — — Bal 55 5.3 — 7.3 0.08 1.4 — — — Bal 60 AWSBNi6 — — — 0.10 — 11.0 — Bal 80 15.2 — — 0.06 4.0 — — — Bal Foils areavailable with more rigid dimensional tolerances as specialty or “A”grades *Maximum concentration

Braze Temp. Density MBF AWS & AMS Melting Temp. ° C. (° F.) (Approx.)g/cm³ Alloy Classifications Solidus Liquidus ° C. (° F.) (lbm/in³) 15965 (1769) 1103 (2017) 1135 (2075) 7.82 (0.283) 20 AWS BNi2/AMS 4777 969(1776) 1024 (1875) 1055 (1931) 7.88 (0.285) 30 AWS BNi3/AMS 4778 984(1803) 1054 (1929) 1085 (1985) 8.07 (0.291) 50 AWS BNi-5a 1052 (1924)1144 (2091) 1170 (2138) 7.70 (0.278) 51 AWS BNi-5b 1030 (1886) 1126(2058) 1195 (2183) 7.73 (0.278) 55 950 (1742) 1040 (1904) 1070 (1958)7.72 (0.279) 60 AWS BNi6 883 (1621)  921 (1688)  950 (1742) 8.14 (0.294)80 1048 (1918) 1091 (1996) 1120 (2045) 7.94 (0.278)

In preferred embodiments, a wire in the inventive welding processpreferably has a similar, or the same, composition as the metal in themetal sheets of the laminate. In preferred embodiments, the wire has anyof the compositions as described above for the metal sheets.

The phase diagram of Ni—P shows a eutectic point near 11% phosphorus byweight in nickel. As the phosphorous diffuses away from the interlayerinto the adjacent metal surface, the local weight percent of nickel isreduced and the composition changes which solidifies the brazeinterlayer. One advantage of the braze process is that the resultingbrazed device can withstand a higher braze temperature because theresultant phosphorous depleted interlayer region will only remelt at ahigher temperature per the phase diagram. Unfortunately, theconventional welding temperature reaches the melt temperature of theparent material (˜1400 to 1500° C. for Stainless 300 series), often anickel containing substance and the result is a remelt of the brazeinterlayer and the formation of cracks. The cracks both create leakproblems for an operational device (heat exchanger, reactor, separationsunit, mixer, or other single or combined unit operation) and mechanicalintegrity problems if the device is intended for high pressure and ortemperature operation. Difficulties with welding over short sections ofbrazed devices and then inspecting, detecting, and repairing cracks hasbeen encountered. This problem becomes even more challenging whenattempting to weld along long sections of a brazed device with hundreds,or even thousands of thin sheets.

One conventional solution to avoid this problem is to braze, rather thanweld, connections to brazed devices.

The invention provides a new use and a new advantage for a weldingtechnique known as cold metal transfer (“CMT”). This technique isdescribed athttp://www.welding-robots.com/applications.php!app=cold+metal+transferas follows:

“Cold” is a relative term in perspective to welding, Cold Metal Transferwelding is commonly referred to as CMT. The workpieces to be joined aswell as the weld zones remain considerably “colder” in the cold metaltransfer process (CMT) than they would with conventional gas metal arcwelding.The cold metal transfer process is based on short circuiting transfer,or more accurately, on a deliberate, systematic discontinuing of thearc, Results are a sort of alternating “hot-cold-hot-cold” sequence. The“hot-cold” method significantly reduces the arc pressure. During anormal short circuiting transfer arc, the electrode is distorted whilebeing dipped into the weld pool, and melts rapidly at high transfer arccurrent. A wide process window and the resulting high stability definethe cold metal transfer process, Automation and robot-assistedapplications is what the process is designed for.

The major advancement is that the motions of the wire have beenintegrated into the welding process and into the overall management ofthe procedure. Every time short circuiting occurs, the digital processcontrol interrupts the power supply and controls the retraction of thewire. The forward and back motion takes place at a rate of up to 70times per second. The wire retraction motion aides droplet detachmentduring the short circuit. The fact that electrical energy is convertedinto heat is both a defining feature and sometimes critical side effectof arc welding. Ensuring minimal current metal transfer will greatlyreduce the amount of heat generated in the cold metal transfer process.The restricted discontinuations of the short circuit leads to a lowshort-circuit current. The arc only inputs heat into the materials to bejoined for a very short time during the arcing period because of theinterruption in the power supply.

The reduced thermal input offers advantages such as low distortion andhigher precision. Benefits include higher-quality welded joints, freedomfrom spatter, ability to weld light-gauge sheet as thin as 0.3 mm, aswell as the ability to join both steel to aluminum and galvanizedsheets.

Additional description of the CMT welding process is presented by Fenget al. in “The CMT short-circuiting metal transfer process and its usein thin aluminum sheets welding,” Materials and Design 30 (2009)1850-1852.

A process known as controlled short circuit (“CSC”) operates similarlyto CMT, and, for purposes of the present invention, comes within theterm “CMT.” Frequency of the wire motion is preferably in the range of10 to 30 Hz, but other frequencies are also useful. In some embodiments,travel speed of the wire along the surface is preferably less than about30 inch per minute; in some embodiments travel speed is in the range of1 to 25 inches per minute or 15 to 25 inches per minute.

The inventive process can be used to seal protruding features inlaminated devices. An example is shown in FIG. 3. As with all aspects ofthe invention, the invention includes structures formed by the methodsof the invention.

Shim Side Repairs

-   -   One option to seal leaks along the shim side of a device, is to        seal along the protruding edges of the shims. As shown in FIG.        3, the CMT may weld in the resultant corner which is 0.125″ away        from the end of the laminate as shown in FIG. 3.        Identify start and stop point of repair based on previously        collected leak test results        Program robot for start and stop points with wire placed about        1.5 wire diameters away from the seam to be repaired    -   Surface preparation:        -   Wire brush seam prior to repair        -   Wipe seam with acetone    -   Set weld parameters:        -   Feed angle=10°        -   Wire feed speed=150 inches per minute        -   Arc Length Value=+3.0        -   Travel Speed=20 inches per minute    -   Run repair and visually inspect to ensure seam was covered        If seam was not fully covered in the known leak zone: grind down        repair and perform second pass        Repeat until all coolant side zone leaks have been welded (see        FIG. 4)        Post repair machining    -   Mill/Grind down repair beads on faces in zones where rings will        be attached to ˜20 mil (500 microns) pad height        Post repair leak check    -   Repeat leak test procedure to ensure that all leaks have been        sufficiently sealed. If additional leaks exist, re-repair as        necessary        The invention includes apparatus in which sheets comprising        channels protrude from a face of a core block. Advantageously,        this design can be combined with welds along the protruded        sheets that have superior leak resistance. In some preferred        embodiments, the protruded sheets are enclosed within an        enclosure of the type described herein.

Example 1

The brazed device was leak checked to confirm the presence of leaks. Thedevice consisted of SS 304L laminates that are brazed with a nickelphosphorous (BNi6) interlayer (0.001″ thick, 25 microns), brazed at 960C for 1 hour with a pressure of 60 lbf per in2 (4 bar). If leaks werefound then they were repaired using Cold Metal Transfer (CMT) welding.SS304L, 40 mil (100 microns) diameter filler wire was used for therepair.

For devices with fins or waveforms or channels that need to be keptclean of weld material, a shroud is placed over such areas prior towelding. It is preferred but not required that shrouds are placed overopenings or sides of a device not undergoing welding while repairing anaffected or leaky face of a device.

Crack repair was accomplished on a device schematically illustrated inFIG. 5.

-   -   Perimeter zone repairs        -   Cover waveform sections preferably with high temperature            ceramic tape to protect them (note: repairs are not            occurring in zones directly adjacent to the copper            waveforms).        -   Identify start and stop point of repair based on leak test            results        -   Program robot for start and stop points with wire centered            over seam to be repaired        -   Surface prep prior to welding:            -   Wire brush seam prior to repair            -   Wipe seam with acetone        -   Set weld parameters:            -   Wire Feed Speed=120 inches per minute            -   Arc Length Value=+3.0            -   Travel Speed=20 inches per minute        -   Run repair and visually inspect to ensure seam was covered            -   If seam was not fully covered in the known leak zone:                grind down repair and perform second pass        -   Repeat until all perimeter zone leaks have been welded            The waveforms can be covered with a metal film to protect            them during welding.

Example 2

Alternate inventive methods for sealing leaks across brazed joints alongshim or laminae. The seam or opening of the channel is welded overdirectly (preferably by CMT). The fully closed channels are thenreopened using machining, plunge electro-discharge machining, MolecularDecomposition Process Grinding MDP, grinding or other process to reopenjust the flow passage ways while leaving the brazed joint fully coveredwith the CMT weld. FIGS. 6-8 illustrate this process. Preferably, thewelds are ground flat prior to machining to reopen the channels. Theillustrated in the figures had a leak rate greater than 0.5 psig loss in15 minutes at 100 psig fixed pressure before repair of the braze leakswith CMT and a leak rate less than 0.5 psig loss in 15 minutes at 100psig fixed pressure after braze repair. This test can be used as amethod to characterize preferred embodiments of the inventive apparatus.In each case, leak testing is conducted with nitrogen gas at roomtemperature.

The invention thus includes a method in which a weld is formed overapertures (channel openings) and weld material is then removed to reopenthe channels—this method has been demonstrated to reduce leaking in alaminated device.

1. Laminated apparatus comprising: a core block comprising sheets ofmetal bonded together, at least in part, by a braze composition disposedbetween the sheets; a welding composition disposed on the core block andadhering to the braze composition; wherein the welding composition has acomposition that differs from the composition of the braze composition;and wherein the welding composition is diffused 2 mm or less into thecore block.
 2. The apparatus of claim 1 wherein the welding compositionforms a continuous weld across more than one metal sheet and more thanone of the braze composition disposed between the sheets.
 3. Theapparatus of claim 1 comprising fluid channels disposed in the sheetsand inlets to the fluid channels disposed on edges of the sheets.
 4. Theapparatus of claim 3 having resistance to leakage such that, when thefluid channels are pressurized with N2 at 100 psig (6.9 bar gauge), thepressure decreases by less than 0.5 psi (0.034 bar) after 15 minutes. 5.The apparatus of claim 3 comprising: a first set of fluid channelswherein each channel comprises an inlet and an outlet; a second set offluid channels wherein each channel comprises an inlet and an outlet; afirst welded inlet manifold, a first welded outlet manifold; a secondwelded inlet manifold, and a second welded outlet manifold; wherein thefirst welded inlet manifold is in fluid communication with the inlets ofthe first set of fluid channels; wherein the first welded outletmanifold is in fluid communication with the outlets of the first set offluid channels; wherein the second welded inlet manifold is in fluidcommunication with the inlets of the second set of fluid channels;wherein the second welded outlet manifold is in fluid communication withthe outlets of the second set of fluid channels; and wherein each of themanifolds are connected to the core block by a welding compositionwherein the welding composition has a composition that differs from thecomposition of the braze composition; and wherein the weldingcomposition is diffused 2 mm or less into the core block.
 6. Theapparatus of claim 5 wherein at least 2 of the manifolds are welded tothe core block on a same side of the core block.
 7. The apparatus ofclaim 1 comprising subassemblies that have been diffusion bonded.
 8. Amethod of conducting a unit operation in the apparatus of claim 1comprising: passing a fluid into a channel in the core block andconducting a unit operation on the fluid in the core block.
 9. Themethod of claim 8 wherein a first fluid is passed into a first set ofinlets and into a first set of channels in the core block; a secondfluid is passed into a second set of inlets and into a second set ofchannels in the core block; and wherein the first fluid and the secondfluid flow in adjacent sheets within the core block and the first fluidexchanges heat with the second fluid in the core block.
 10. A method ofwelding a metal onto laminated apparatus, comprising: providinglaminated apparatus comprising sheets of metal bonded together, at leastin part, by a braze composition disposed between the sheets; applying ametal onto the laminated apparatus by a welding technique wherein a wiremoves in a reciprocating motion and wherein a spark is generated whenthe wire touches and/or is pulling away from the laminated apparatus;and wherein molten metal is applied to the surface while the wire movesaway from the surface.
 11. The method of claim 10 wherein, within 30seconds of active welding, and without liquid cooling, the temperatureof the laminated article is 100° C. or less (preferably 50° C. or less)throughout the entire apparatus.
 12. The method of claim 10 wherein aweld is formed at a rate of 25 cm per minute or greater.
 13. A method ofrepairing a crack comprising applying a metal according to the processof claim 10 onto a crack in laminated apparatus. 14-19. (canceled) 20.The apparatus of claim 1 further comprising a solid-walled enclosurethat encloses plural apertures within a single, contiguous space on aside of the core block; wherein the solid-walled enclosure comprises asolid, continuous wall that is welded on one side to the core block bythe welding composition.
 21. A process of operating the apparatus ofclaim 16, comprising: opening the manifold while leaving the enclosurewelded to the core block; and performing service on the core block. 22.The process of claim 21 wherein the step of performing service comprisesat least one of: regenerating catalyst, replacing catalyst, regeneratingsorbent, replacing sorbent, cleaning, or diagnostic testing.
 23. Themethod of claim 8 wherein the unit operation comprises a Fischer-Tropschreaction.